PERFORMANCE BRAKE UPGRADES: Acceleration and organ-squeezing cornering is fun, but so is stopping when you want to. Here's a look at what products are out there
Let's face it -- the primary reason that many street enthusiasts upgrade to a snazzy aftermarket braking system is to enhance appearance. After all, when you slap on a set of very open-spoke, big-diameter custom wheels for them, they don't want to stare at some crummy looking (and rusty) OEM cast calipers and boring discs. It's akin to donning a top-shelf Armani suit mated with a pair of grungy hiking boots. It simply won't do.
So, you convince them to swap over to a set of color-coded alloy calipers mated to racy-looking rotors that feature slots or cross-drilled holes. Hmm... or maybe rotors that are mated to satin or polished aluminum hats for a finishing touch.
From the standpoint of performance function, however, the justification to upgrade is much more substantial for two primary reasons.
1. The customer needs to be able to haul that puppy down in short order when needed, with dependable repeatability (after all, if you have a performance engine and suspension, you'll likely play once in a while).
2. If a set of large-diameter, super-plus-size wheels and beefy tires have been added to a vehicle, the existing brakes may not be able to handle the increased amount of rotating mass.
If the customer wants an upgrade, the choices you can offer him or her in terms of calipers, pads, rotors and brake hoses today are plentiful.
Instead of upgrading calipers alone, it's always best to sell a rotor/caliper system in order to help the driver achieve optimum performance. With that said, his choice in calipers is enormous. Yes, he could stick with OE single-piston sliding calipers, but what fun is that? A solid-mounted (as opposed to sliding) caliper is much more efficient and is much more capable of handling performance braking requirements. A fixed (rigidly mounted) caliper will feature two, three, four, six or more individual pistons (all the way up to eight or more).
Today's elite aftermarket calipers, in addition to providing outstanding performance, are mouth-watering cool in appearance. Primarily constructed of lightweight alloys, the shape is appealing, and the finishes and color availability allow you to give the customer exactly the look he wants. Typical finishes include polished, satin aluminum, black, red, silver, and yellow (depending on the maker, additional color choices may be offered).
If your customer's vehicle came from the factory with single-piston sliding calipers, don't worry. Chances are a high-end aftermarket supplier offers a bolt-on kit that will include adapter mounting brackets that accept the new bolt-on/fixed calipers.
Disc pad availability today is very diverse, with a compound/makeup suitable for every application (moderate use, high performance use, racing applications, heavy-duty use, etc.). We certainly don't have room here to discuss every brand or type. Suffice it to say that whatever your needs are, there's a pad out there that will fill the bill.
Many of today's high performance and ultra-high performance pads feature makeup involving ceramics, various metals, carbon fiber, etc. The best avenue is to select the pad that is recommended by the pad maker or rotor maker for your specific application and intended use.
For racing applications, it's important to help these niche customers select a material that will provide stable grip under specific racing scenarios. For example, a relatively "softer" compound might be recommended for short-track use, while a "harder" pad with improved thermal transfer might be the ticket for endurance racing.
For the street, the only reason a customer will choose rotors that feature drilled holes or slots is for appearance (especially where a set of open-spoke custom wheels reveal the rotors). However, there are functional reasons for drilled holes or slots, which may help you sell them. They also:
1. help dissipate heat and reduce brake fade.
2. provide an escape path for gasses that are generated between the pads and rotor (which aids in pad efficiency).
3. promote self-cleaning of the pads.
4. reduce unsprung weight.
5. increase thermal stability of the rotors, which reduces the chance of the rotor warping.
Rotors are available that are drilled, slotted, or with a combination of holes and slots. If a rotor is cross-drilled, this alone won't dictate direction of rotor rotation. A rotor will be directional based on vane type or, in the case of some slotted rotors, the angle of the slot cuts. Always confirm this by checking the rotor manufacturer's instructions.
For street use at legal speeds, the enhanced appearance is definitely a plus, so as long as you're replacing rotors, why not promote a design that provides both form and function?
Rotor venting (the vanes seen around the disc perimeter) is intended to evacuate heat. Note that a rotor that features angled (curved) vents are directional, with the vent angle positioned to "pump out" excess heat. Never install a curved-vent rotor backwards.
The bigger the rotor diameter, the better, right? Well, maybe. The entire braking system (and rotors are no exception) must be designed for the specific vehicle and its intended use. Pad and rotor packages are designed to work best within an optimum temperature range. If the rotor is too small, there won't be enough surface area to handle the heat generated during pad contact. If the rotor is too large, the pads may not reach their optimum working temperature. So while bigger rotors may look sexy, don't let your customers get carried away. Help them select a rotor/caliper/pad system that's designed to work best on their specific vehicles.
Car enthusiasts expect you to be the expert when it comes to everything from calipers and pads and rotors to brake fluids and hoses. Brake fluids, in particular, are commonly misunderstood and, frankly, are routinely ignored. So here's everything you want to know about brake fluids.
The "dry" boiling point indicates the temperature at which fresh, uncontaminated brake fluid will boil (when there's no moisture in the system). The highest-rated DOT 3 brake fluid that's available today offers a dry boiling point of 572 degrees Fahrenheit (most common DOT 3 fluids are rated at 401 degrees F; while most DOT 4 fluids are rated at a minimum dry temperature of 446 degrees F).
The "wet" boiling point is the temperature at which brake fluid will boil once fully saturated with moisture. A DOT 3 brake fluid's wet boiling point is required to provide a minimum of 284 degrees F. DOT 3 and 4 fluids are all glycol based. Over time, moisture will enter the system (it's unavoidable) due to condensation and ambient humidity. DOT 3 and 4 brake fluids are glycol based, and are hygroscopic (meaning they will gradually absorb moisture). Contrary to popular belief, a glycol-based brake fluid's ability to absorb moisture is actually a good thing, as compared to a silicone fluid that carries moisture.
Silicone brake fluid (DOT 5) has its appeal and advantages. There's nothing inherently wrong with silicone brake fluid, but we need to understand its pros and cons.
It won't damage a painted surface (which is why many collector/custom car/street rod owners opt for this grade of juice). Silicone brake fluid also won't absorb atmospheric moisture, which leads many to believe that this will absolutely prevent brake system internal corrosion. Let's clear up a few things.
While DOT 5 silicone fluid (generally rated with a dry boiling point of about 500 degrees F) won't absorb moisture (it's non-hygroscopic), it can still carry moisture on its surface. This can lead to beads of moisture being pushed through the lines and being deposited in the calipers.
Since caliper temperatures can exceed 200 degrees F, and since the boiling point for water is 212 degrees F, any collected moisture can boil, causing brake system failure. So, in terms of preventing system corrosion, it's not a magic pill.
Another major disadvantage of silicone fluid is its propensity to aerate, or foam, when subjected to quick and repeated pressurization. For that reason, you must never add silicone brake fluid to any vehicle that is equipped with an anti-lock brake system. If you opt to use silicone fluid in a vintage car or a street rod that is only street-driven in a sane and legal manner, chances are it'll be fine.
If he intends to push the vehicle (hot rodding it or racing) where he'll need to modulate the brake pedal repeatedly, it isn't the best choice, since the driver may experience a spongy and less-than-responsive brake pedal. And, be aware that in some cases, the use of an all-silicone hydraulic system may provide a slightly spongy pedal upon initial activation.
Also, never mix silicone fluid with a glycol based-fluid. If your customer is changing from one to the other, fully flush the system and fill only with the fluid he intends to use.
New brake fluid formulations are available using a synthetic formula (not silicone, though) that offer higher boiling points.
Oooh, la, la! A progressive look at calipers
For street performance applications, four-piston (and in some cases, six-piston) calipers are pretty much the accepted norm. Piston diameter is based on the manufacturer's design in terms of master cylinder volume (as a general rule, the combined piston volume should match the master cylinder's bore size and brake pedal leverage ratio). In most cases, the pistons will be of identical diameters.
However, calipers are also available with progressive-diameter pistons, where the caliper may feature a combination of small and larger diameter pistons. If this is the case, the end of the caliper with the smaller pistons must be positioned at the rotor entrance of the caliper, with larger pistons at the rotor exit.
This progressive small-to-large piston diameter layout is designed to equalize pad wear to prevent taper wear (the larger pistons provide more clamping force than the smaller pistons). Basically, this allows a lighter clamping force as the pads attack the rotor, transitioning to increased clamping force as the rotor passes through the pad area.
If the calipers feature a combination of piston sizes, this makes the caliper directional. If you flip it around, you'll promote tapered pad wear.